1. Field of the Invention
The invention relates to a light detecting system, and more particularly, to a light detecting system for detecting light projected from a projector.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2 FIG. 1 is a perspective view of a prior art light detecting system 50 and a projector 52. FIG. 2 is a front view of the light detecting system 50 in FIG. 1. The light detecting system 50 is used for detecting light projected from the projector 52. When the projector 52 is initiated, it will project a picture image forward. The light detecting system 50 comprises a frame 54 positioned at a predetermined position in front of the projector 52, thirteen light sensors 56 fixed on the frame 54 for detecting the picture image, a control device 60 connected with the projector 52, and a screen 58 installed on the frame 54 to form a surface with a position mark. The control device 60 is used to output an image signal to the projector 52 so that the projector 52 can project a picture image onto the screen 58. The position mark on the screen 58 is used to calibrate the position of the picture image on the screen 58.
The screen 58 has five equally spaced vertical lines 53A, 53B, 53C, 53D, 53E and five equally spaced horizontal lines 55A, 55B, 55C, 55D, 55E. The vertical and horizontal lines form a number of intersections on the screen 58. Thirteen of these intersections are defined as sampling positions. The thirteen light sensors 56 are installed at corresponding sampling positions for detecting light emitted from the projector 52 so as to calculate various parameters of the picture image such as average luminous flux, light uniformity, color temperature, color coordinate, color balance, color uniformity and color contrast ratio.
Because the light sensors 56 are very expensive and the light detecting system 50 uses thirteen of them, the cost of the light detecting system 50 becomes extremely high. Moreover, the light sensors 56 are fixed on the screen 58, therefore the number of sampling positions cannot be increased when more detailed analysis of the picture image is required.